When mine were the original colour I couldn't get a code when I wanted a refurb so in the end I chose what I thought was a better looking colour on a silver car thinking that if it looked good and they were all the same colour that would be fine. Understand you wanting to maintain originality though.
I'd be interested to know what you settle on, I'll keep a note of it in my file when you find out.
When you've done this you may want new centre caps...they're around £15 each!
This is what mine look like...
